Genetics Flashcards
What is genetics?
Study of heredity that deals with heredity and variation of organisms
Scrutinizes the functioning and composition of the single gene.
What is a gene?
A unit of heredity; a section of DNA sequence encoding a single protein
What constitutes a genome?
The entire set of genes in an organism
Define alleles.
Two genes that occupy the same position on homologous chromosomes and that cover the same trait
What are chromosomes?
Structures formed by DNA and proteins that house multiple genes in the cell nucleus
What is DNA?
The molecule that forms genes, grouped into chromosomes
What does homozygous mean?
Having identical genes for a particular characteristic
What does heterozygous mean?
Having two different genes for a particular characteristic
What is dominance in genetics?
The allele of a gene that masks or suppresses the expression of an alternate allele
What is a recessive allele?
An allele that is masked by a dominant allele; does not appear in the heterozygous condition
What is a genotype?
The genetic makeup of an organism
What is a phenotype?
The physical appearance of an organism
What is Mendel’s Law of Dominance?
Some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effect of the dominant allele
What does Mendel’s Law of Independent Assortment state?
Genes of different traits can segregate independently during the formation of gametes
What is Mendel’s Law of Segregation?
During gamete formation, the alleles for each gene segregate from each other
Define autosomal dominant inheritance.
Occurs when either or both parents have a dominant gene of the disease
Characteristics of autosomal dominant inheritance include:
- Sex of affected individuals is not important
- Family history of the disease
- Vertical transmission
Define autosomal recessive inheritance.
Disorder occurs only if two genes for the disease are present (homozygous recessive)
Characteristics of autosomal recessive inheritance include:
- Both parents are clinically free of the disease
- Sex of the affected individual is not important
- A known common ancestor may exist
What is X-linked recessive inheritance?
Inheritance of the genes from both parents is incompatible with life
Characteristics of X-linked recessive inheritance include:
- Only males have the disorder; females are carriers
- History of girls dying at birth
- Sons of affected men are unaffected
What is X-linked dominant inheritance?
Disorders where the affected gene(s) is/are transmitted only by the X chromosome
Characteristics of X-linked dominant inheritance include:
- All individuals with the genes are affected
- All female children of affected men are affected
- It appears in every generation
What is multifactorial or polygenic inheritance?
Disorders caused by multiple factors with the involvement of more than a single gene
What are genetic disorders?
Congenital abnormalities resulting from a defect in the structure or number of genes or chromosomes
What are some risk factors for genetic disorders?
- Pregnancy over age 35
- Family history of genetic disorders
- Exposure to drugs
What is Cystic Fibrosis?
A lethal genetic disease affecting Caucasians caused by a mutant recessive gene
What is the probability of getting Cystic Fibrosis if both parents are carriers?
1 in 4 children may be affected
What is genetic counseling?
Process that provides information regarding the risk of developing or transmitting a genetic condition
Aims of genetic counseling include:
- Increase understanding of genetic diseases
- Identify psychosocial tools needed
- Reduce family anxiety
Indications for genetic counseling include:
- Maternal age >35 years
- Paternal age >40 years
- Family history of birth defects
